Abstract:Endophytes were isolated from six medicinal plants with antioxidant activity, namely, Aconitum carmichaelii, Thalictrum aquilegifolium Linn., Angelicae pubescentis Radix, Plantago asiatica L., Mentha haplocalyx Briq, and Alisma orientale. The active antioxidant ingredients from the fermentation broth of endophytes and mycelium extract were studied. Potato dextrose agar (PDA) medium and Gauze’s medium were used to isolate the endophytic fungi and endophytic actinomycetes, respectively. The antioxidant activities of all extracts were measured, the total phenolic and total flavonoid content of the extracts from those endophytes were compared, and high-activity strains were identified using morphological and molecular biological methods. Finally, 43 endophytic fungal strains and 18 endophytic actinomycete strains were isolated. Among them, the endophytic fungi had good antioxidant activity, and six strains (9.84%) showed a strong ?OH free radical scavenging capacity (clearance rate ≥70%). The ethyl acetate extract of the fermentation broth of DHL-10 strain showed strong antioxidant activity; its half maximal inhibitory concentration (IC50) value for hydrogen peroxide radical scavenging was 0.26 mg/mL, and total phenolic and flavonoid content were up to 0.81±0.05 mg/g and 0.84±0.05 mg/g, respectively. DHL-10 strain was identified as an Alternaria sp. by morphological and molecular biological methods. Our results demonstrate that the endophytes from medicinal plants are good sources for active antioxidant substances.
